Nest Help

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  #1  
Old 09-02-19, 09:28 AM
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Question Nest Help

I have installed a 3rd Gen Nest on my home system, and my son wanted one on his. Confirmed compatibility (Trane XV80) and wiring from funace to thermostat,,, then caonnected. Nest showed the wiring was incorrect, so contacted Nest. Told them what was going on and the furnace made wierd noise when powered. Asked me to disconnect R wire and check voltage on R wire. ( 26 Volts ), Nest then told me to reconnect R and cap C wire. Everything worked ???? But everything I read says I need a C wire .... HELP !!!
 
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  #2  
Old 09-02-19, 11:04 AM
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You need a C wire.
Nest will tell you that you don’t but you do.
Welcome to the beginning of the issues the Nest causes. Probably the worst possible choice one can make for a thermostat. I’ve made many $$$$ through their problems.
You’ll have to make sure the common is connected on the other end.
 
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Old 09-02-19, 12:22 PM
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Hi, check voltage from Red to what ? How many conductors are between Tstat and furnace?
Geo
 
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Old 09-02-19, 12:48 PM
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Why does it work fine with out a C Wire and chatter when the C wire is connected ?
 

Last edited by Braeburn94; 09-02-19 at 12:49 PM. Reason: spelling
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Old 09-02-19, 12:51 PM
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It starts working off if it’s internal batteries without a common. When it goes to recharge the batteries it can cause short circuits that make the blower constantly run, heat/cool run uncontrollably, even short out and damage electronics in the hvac equipment.
I have no reason why it chatters with the common attached. Perhaps maybe a shorted subbase.
 
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Old 09-02-19, 12:55 PM
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Sorry, checked voltage between G and Rh Green wire and red wire, Wires available are Yellow, Green, White, Brown , Blue and Red.
 
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Old 09-02-19, 01:02 PM
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Could also have a sort in the conductor wire, or even a broken conductor.
More then likely the problem is with the Nest.
I don’t want to seem hateful but you couldn’t pay me enough to have one of those things in my house.
 
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Old 09-02-19, 02:07 PM
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Welcome to the forums.

In the future..... take a picture of the old wiring. A picture says a thousand words.
Available....I have..... Yellow, Green, White, Brown , Blue and Red.
We know R is red and G is green. What are the colors used for ?
If you don't know..... look at the control board in the blower area of the furnace.
 
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Old 09-02-19, 02:34 PM
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Sorry Pete, Got some one telling me the Nest is the worst product ever and not being very helpfull... So back to you. Yellow is Y1 , Green is G or fan, White is to W1, Brown is to W2 Aux, Blue was to Common, Red is to Rh.
Connected all correctly and checked board connections on Trane HV80 unit.... all the same. As I said, when common is connected funace pulses like it;s trying to start but nothing, When I capped the blue wire, every thing worked fine. My concern is with out a common will the nest battery hold up even thouugh nest says it will charge using the Rh and Rc lines
 
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Old 09-02-19, 03:30 PM
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Hi, test between R&Blue (common) at the Tstat .
Did you label the way the old Tstat was wired?
Geo
 
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Old 09-02-19, 03:30 PM
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I’m sorry you found me unhelpful, but in 18 years of professional hvac service there hasn’t been a worse thorn in my side then the Nest. It irks me to have such an expensive product that works so poorly.
But as I said in a previous post, is the common even hooked up on the other end? You can also ring the wires out with your meter.
Just remember, electricity knows no color.
 
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Old 09-02-19, 04:17 PM
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Test for what ? And I have a photo on my phone showinng the wiring of the old themostat ...
 
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Old 09-02-19, 04:26 PM
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It sounds like your wiring is correct. If you verified it at the furnace board..... then that's what it is.
You could check for voltages to confirm everything.
At the stat......
R - C is 24vAC.
R - Y1, W1, W2, G should all be the same..... 24vAC.

You could have a defective nest sub base. I've seen a high number of base defects. Nest will usually ship one out no charge. That nest will run on most systems without a C connection. You could certainly try it to see if there is a charge problem. You can also check the charge/battery voltage in the nest itself.
 
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Old 09-02-19, 06:56 PM
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Thanks, I have checked the wire voltages and all is well. Also checked a the operating voltages (battery etc.) on the set up power
menu. All voltages seem to be at or above recommended. Going to have my son monitor that screen for any changes....

Thanks again ...
 
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